Dry ice refrigeration



Nov. 5, 1935. D. MCNEH.

v DRY ICE REFRIGERATION Filed Jan. 16, 1932 INVENTOR.

z//vc/M/ 10A/f; L BY ATTORNEYS.

Patented Nov..a hg l hdlddd Duncan McNeil, dan Francisco, (Balli. assigner to Chas. E.. McCormick Lumber 6o.., San Fran cisco, Calif., a corporation oi Delaware This invention relates to refrigeration and has Fig. 1 is a diagrammatic plan oi a cold storage room equipped with apparatus in accordance with my invention,

Fig. 2 is an emerged diagrammatic view ci the controls and associated pipes.

liig. 3 is an enlarged elevation oi one oi the dry ice containers shown in plan in Fig. l.

Fig. i shows a thermostat directly connected to a gas escape control valve.

Before describing the apparatus, it would be well to draw attention to the fact that il dry ice is placed in a food chamber, its evaporation will quickly lower the temperature of the space within the chamber and also lill the space with COagns which tho desirable in the preservation oi some kinds of food would prevent entrance oi' a person into the room, unless the room were vented.

Besides this, the temperature oi the room would not be under control, ior ii the air of the room could freely reach the dry ice to transmit its heat thereto, the temperature would drop en cessively.

By my invention l control both the tempera1 ture oi the' room and also provide for admission oi some CO2 gas to the room or tor its total en clusion as may be desired.

lilly invention is based on my discovery that ii the dry ice is Within a closed receptacle to which heat can only gain access by slow circulation ci air within the heat insulated cold storage space, that the rate of its evaporation can be controlled by closing or opening a gas vent pipe leading troni the receptacle out ci the cold storage room prel=a eraloly to the outer air. llt would be dangerous to close such a vent ii the receptacle were in a heated zone, but ii' in an insulatedspace, and the temperature of said space has been lowered to proper degree for cold storage, generally a ieu degrees above freezing, then it is no longer dangerous to close or substantially close the gas vent as the available heat for transfer to the dry ice is much less, and as a slight pressure oi gas builds up in the receptacle it further retards the absorption oi heat by the dryA ice within.

ln practice, l have round that with large cold storage rooms, using an initial charge oi a thereI sand pounds oi dry im, and with the gas vent outwardly controlled by a thermostatic valve set to the temperature desired, a substantially uni form temperature of say 34 li'. may be automat ically maintained for many days, as shown loy a recording thermometer, and at a cost much less in case of the room size bores than would be the case ii a mechanical refrigerating plant were in 5 stalled, drst cost and unkeep considered.

In the drawing Fig. 1 is a plan of a cold stuns age room i having thick heat-insulated walls i?, and which room is provided with a door d for the placing and removal of food material, and l0 the room vmay communicate with one or more similar rooms i as by a door d.

No importance attaches to the room construe tion other than it should be well insulated lilre any nrst class cold storage room or ice bon conl5y struction.

Within the room and preierably suspended from the ceiling t at a distance ci a few inches, are several dry ice receptacles il (one tvill be enough il oi sumcient size or the rooin or box is do small).

IThese receptacles are preferably made oi sheet metal such as heavy galvanized iron and are suspended from the ceiling on straps l. Each receptacle has a door d at one side or one end 2li which is provided with clamping handles t and also with a sealing strip or gasket, not shown, so as to close substantially gas=tight. Frein the top oi each receptacle leads a pipe i@ connected one to the other and to a pipe ii for escape oi so the gas to the outer atmosphere through a vent pipe i2 under control oi a pressure regulating valve li'to be later-described.

Returning to the dry ice receptacles, these may be cylindrical to better withstand pressure, or 35 simply heavy rectangular sheet steel hoses as shown, and it is desirable that they be dtted ers teriorly with heat transmitting hns id oi sheet metal, those at the ends or sides ci the recep tacles being here shown cut upward at an angle lo so as to reduce the danger oi a person striking their corners, yand this applies also to the outer corners of all hns used on the receptacles.

lt is also dirable that the receptacles have supporting ribs or a perforated ialse bottom ill a5 to support the dry ice so that the gas pressure may act evenly about it.

0n any oi the gas piping within the cold storage room is a gas bleeder valve it `for bleeding a small or controllable amount of CO2 gas to the 5o room it desired, and which valve is manuallyoperated by a suitable rod il, or other devicen from a point it outside oi the room.

@ne of the primary objects of the invention is to control the degree oi cold by automatically gg lili closing od or opening up the gas escape pipe il, opening it when the temperature rises too much so as to induce quicker evaporation, and closing it to restrict evaporation as the temperature falls, and this y be accomplished in various ways with existing pressure control apparatus operated by a suitable temperature responsive device or thermostat placed in the cold chamber, such for instance as a direct houle-up between an expanding and contracting thermostat with a valve on the gas escape pipe il, as shown in Fig. d wherein thegas escape pipe, designated i i', is tted with a control valve ld pivotally and adjustably connected at 2t with the metallic bellows 2i or other movable member of a thermostat here shown as a gas or liquid bulb 2t conveniently mounted on said pipe or ceiling and exposed freely tothe temperature oi the cold storage room. Such a thermostat could'be set to produce any desired result by moving its mounting either 'way along the pipe or adjusting the connection. 2t to change the relation of the bulb to the valve it. Such a control may be entirely within the cold storage room with only the vent pipe i2' projecting out into free air for escape oi the gas.

Or, instead of such a direct thermdstatic control oi the evaporation p'pe, a power actuated control may be employed, one such being indicated in Figs. l and 2 wherein the gas passes from pipe il through a diaphragm type pressure regulator it the valve di normally held almost closed by spring 2d, adjustable by a screw 25, and the diaphragm 2t oi which regulator is exposed on its opposite side to air pressure from a small pipe 2l delivered through pipe 2l' from any suitable source of compressed air and passing through any. suitable thermostatically controlled regulating valve set 2d, the thermostat of which is here indicated as a gas bulb 29 positioned within the storage room and its tube 30 extending to the set. Since a number of such control sets or temperature control instruments with or without temperature recording disks or tapes, either spring or electric driven, or mere relay valves, are readily available on the market no detail of it need herebe given, suiiice to say that responsive to increased.

temperature of the bulb 29 it will admit an increased air pressure through pipe 21 against the diaphragm to open the valve 3 i, and vice versa, by breaking the pressure ascthe temperature falls so that when the temperature of the room is lowered to the minimum for which the instrument is set the valve 3i willbe closed, or substantially so. -A safety Valve 32 may be connected across the control instrument to guard against the accidental accumulation oi a dangerous pressure amarte in the receptacles. Also, in case a reading or recording thermometer is not incorporated in the control set, it may be installed in the side of the room as at 33.

if desired to' operate more than one cold storage s 'give the degree oi cold required, and which has )lo been proven from recording thermometers 232i' either incorporated in the control set 2@ or sepa, rately mounted as at to the maintained sub= stantially constant after the desired temperature was reached.

Having thus described my invention, what l claim is:

l. Apparatus for cooling a cold storage c`= ber comprising a closed receptacle for dry ice positioned in thermal Contact with the air oi said 25 chamber, a gas escape pipe leading from the ice receptacle out of the chamber, and means operable from without the chamber for permitting escape oi some gas generated by the evaporation of the ice to said chamber.

2. Apparatus for cooling a cold storage cham ber comprising a plurality of receptacles for dry ice, means for closing the receptacles, interconnected gas escape pipes leading from said receptacles, and temperature responsive means exposed to the temperature of Said chamber con= trolling the escape of gas from said pipes, the means controlling the escape of gas including a pressure regulator on the gas escape pipes, c. compressed air pipe arranged for varying the 40 regulator, and means operated by the temperature responsive device for varying the air pressure.

3. Apparatus for cooling a cold storage chamber comprising a closed receptacle for dry ice positioned within said chamber, a gas escape pipe leading from the ice receptacle out of the chamber, a valve on said pipe for controlling the escape of gas from the receptacle, power means for actuating said valve, and temperature-responsive means exposed to the temperature of said chamber for actuating said power means for opening said valve at a predetermined rise in the temperature of the atmosphere within said chamber, said power means and valve disposed outside the coldstorage chamber.

DUNCAN MCNEIL. 

